Epoxy Resins
Co-Reactant or Hardeners
Types: Polyamide, Aromatic Amine, Amidoamine, Aliphatic Amine, Cycloaliphatic Amine, Aliphatic Amine Adduct
Epoxy coatings are generally packaged in two parts that are mixed prior to application. The two parts consist of 1) an
epoxy resin which is cross-linked with 2) a co-reactant or hardener. Epoxy coatings are formulated based upon the
performance requirements for the end product. When properly catalyzed and applied, epoxies produce a hard, chemical
and solvent resistant finish. They are typically used on concrete and steel to give resistance to water, alkali and acids.
It is the specific selection and combination of the epoxy component and the hardener component that determines the
final characteristics and suitability of the epoxy coating for a given environment.
FEATURES
Common Types Viscosity Flexibility Chemical Resistance
Bisphenol A Bisphenol F Phenolic Novolac Moderate – High Moderate Moderate – High Moderate Low – Moderate Low Moderate Moderate High
FEATURES [co-reactants and hardeners rated top to bottom from best suited to least suited]
Film Flexibility Adhesion
Chemical Resistance
Acids Solvents Water
Best Polyamide Amidoamine Phenalkamine Cycloaliphatic Amine Aromatic Amine Aliphatic Amine Adducts Aliphatic Amine Best Polyamide Phenalkamine Amidoamine Cycloaliphatic Amine Aliphatic Amine Aliphatic Amine Adducts Aromatic Amine
Best
Aromatic Amine Cycloaliphatic Amine Aliphatic Amine Aliphatic Amine Adducts Amidoamine Phenalkamine Polyamide
Best
Aliphatic Amine Aliphatic Amine Adducts Cycloaliphatic Amine Aromatic Amine Polyamide Phenalkamine Amidoamine Best Polyamide Phenalkamine Amidoamine Cycloaliphatic Amine Aromatic Amine Aliphatic Amine Aliphatic Amine Adducts
Blush Resistance Color Stability Low Temp. Application Corrosion Resistance Viscosity
Best Polyamide Phenalkamine Amidoamine Cycloaliphatic Amine Aromatic Amine Aliphatic Amine Adducts Aliphatic Amine
Best
Polyamide Amidoamine Cycloaliphatic Amine Aliphatic Amine Adducts Aliphatic Amine Phenalkamine Aromatic Amine Best Phenalkamine Aliphatic Amine Aliphatic Amine Adducts Cycloaliphatic Amine Polyamide Amidoamine Aromatic Amine Best Polyamide Amidoamine Phenalkamine Cycloaliphatic Amine Aliphatic Amine Adducts Aromatic Amine Aliphatic Amine Best Cycloaliphatic Amine Aliphatic Amine Amidoamine Aromatic Amine Aliphatic Amine Adducts Phenalkamine Polyamide
Common Causes for Irregularities and Finish Defects
Polyamide/Amine Blush
or Surface Enrichment
Occurs when the proper cure cycle of catalyzed epoxies is interrupted or slowed. The “lighter” polyamide or amine hardener separates from the epoxy and floats to the surface where it oxidizes and turns yellow or brownish in color.
Check By:
The polyamide/amine blush can be confirmed by rubbing the surface lightly with a clean rag saturated with MEK or Reducer R7K54. The yellow appearance will be removed, but may later return.
Caused By:
Improper Mixing
■ Areas rich in polyamide or amine content may exhibit yellowing/blushing and/or an oily exudate
■ Areas rich in epoxy content will appear normal in color for a period of time, but may eventually discolor
■ May result in color variations along the same coated surface ■ Drying and curing times may be affected
Improper Hardener
Epoxy coatings are formulated with optimum levels of a hardener for a given level of epoxy resin. This ratio differs from product to product. The use of an improper hardener may result in an undercatalyzed or overcatalyzed product.
Undercatalyzed Films:
■ May appear dry but will not fully cure ■ May appear soft and gummy
Overcatalyzed Films:
■ May be hard and brittle
■ Both will result in discoloration, yellowing, and reduced performance properties
Insufficient Induction (Sweat-In Time)
Many epoxy coatings require a specified induction time in order to fully “compatibilize” the epoxy resin and the hardener. When required, this pre-reaction will reduce the likelihood of poor film appearance and poor coating performance. Lower temperatures and/or high humidity will generally require longer induction periods.
Improperly inducted epoxies will exhibit:
■ A lower gloss than expected
■ Yellowing becoming progressively worse over time ■ Polyamide/amine blushing
■ Reduced chemical resistance ■ Softer film
■ Color float and/or color variation
It is possible that the coating material applied initially may develop low gloss and discolor, while the rest of the surface, painted with the same material, will appear normal as induction time has increased.
Low Temperature
Most epoxies are formulated for application at temperatures above 50–55°F. Temperatures below 50°F will stop the rate of the chemical reaction between the epoxy and the hardener. The evaporation of the solvents in the coating are also inhibited.
■ Both of these conditions will increase the likelihood of blushing, discoloration and down-glossing.
■ Be aware that surface temperatures may be much lower than the air temperature. Epoxy coatings should never be applied below the recommended temperature range, or when temperatures are expected to fall below the minimum recommended temperature during the first 72 hours of cure.
High Humidity, Moisture Condensation, Stagnant Air
■ Most epoxies are designed for application up to a maximum 85% RH.
■ High humidity and/or the presence of moisture may cause discoloration or a “greasy” feel and poor uniformity of appearance. ■ The polyamide/amine may separate and cause discoloration. Maximum effort should be made to increase fresh air circulation to minimize this effect.
Insufficient Curing of
Water-Based Primers or Fillers
If water-based primers are not sufficiently cured prior to topcoating, moisture migrating through the fresh epoxy film will inhibit the drying and curing of the epoxy. This will cause discoloration, low gloss and possibly delamination.
Common Causes for Irregularities and Finish Defects
Discoloration from Exposure UV Light (Sunlight)
■ This is a surface phenomenon attributed to the natural darkening of epoxy resin upon exposure to UV or sunlight. This problem occurs most often in areas with intermittent sunlight, creating a “checkerboard” effect.■ The discoloration may be confirmed by scraping away the surface layer with a knife to expose the underlying film which will appear lighter in color.
Discoloration from Chemical Exposure
■ Certain chemical compounds, such as carbon monoxide and carbon dioxide, are known to react with freshly applied epoxy films and cause discoloration. This discoloration will be more pronounced in areas of high film build and in areas with little or no air circulation. ■ Check area for cleaning agents that may contain these
compounds. Animal kennels or shelters are also suspect because of waste byproducts.
Epoxy Finishes: Resistance to Yellowing
PRODUCT [epoxies rated top to bottom from best resistance to least resistance]Polysiloxane XLE-80
Pro Industrial Hi-Bild Waterbased Epoxy Water-Based Catalyzed Epoxy
Tile-Clad HS Epoxy
Water-Based Tile-Clad
Pro Industrial High Performance Epoxy Epolon II Multi-Mil Epoxy
Macropoxy HS Epoxy
Macropoxy 646 Fast Cure Epoxy High Solids Catalyzed Epoxy
Macropoxy 846 Winter Grade Epoxy Sher-Glass FF
Tank Clad HS Epoxy Duraplate 301
Dura-Plate 235
Best Resistance
Key Issues to Consider During Selection and Use of Epoxies
Substrate Types. Steel, concrete, etc. Is it suitable for the coating
and the environmental exposure?
Surface Prep. Are the requirements adequate?
Temperature/Variations. Normally above 55°F for the first 72 hours
of drying, and at least 5°F above the dew point.
Humidity. Normally below 85% required.
Environmental Exposure. Is the coating suitable for the conditions it
will be exposed to?
Performance Requirements. What performance characteristics
will the coating be exposed to? (i.e. abrasion, flexibility, heat resistance, etc.)
Recoatability. Will it be required and within what time frame? Application Methods. Is the coating designed for the specific
method? (i.e. spray, brush, roll, squeegee/trowel)
Cost/Value Considerations. Cost per mil per square foot per year
of life expectancy.
Film Build. Is the coating able to comply with the specifications? Air Movement. It is very important to have fresh air circulating over
the surface during drying.
Induction Time. Critical, especially during cold weather and
high humidity.
Pot Life. Do not exceed. Coating may appear usable but will exhibit
poor performance.
Aesthetics. Be aware that some epoxies yellow more than others.
More noticeable in whites and off-whites.
Odor. Will odor be a concern in or around the application area?
Solvent-based, water-based, high solids epoxies.
Epoxies: Common Problems and Most Probable Causes
Common Problems
Most Probable Causes
Surface Contamina tion Applica tion Method Exceeded P ot Life
High Humidity Improper Hardener Swea
t-In T
ime
Recoa
t T
ime
Tint Level Improper Mix Ra
tio
UV Light Exposure Absence of Light Exposure to Chemicals Wrong Reducer Solvent Percent Reduction Moisture/Condensa
tion
Product Selection Applica
tion T empera ture Surface T empera ture Initial Tempera ture 72 Hrs.
Film Thickness Air Movement Batch V
aria
tion
Primer Surface Prepara
tion
Discoloration/Yellowing
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Blushing
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Exotherm (Hot Paint)
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Poor Intercoat Adhesion
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Soft Film
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Tacky Film/Slow Dry
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Lifting/Wrinkling
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Bleeding
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Pinholing
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Cratering
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Low Film Thickness
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Sagging
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Cracking/Crazing
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Epoxy Coating Comparison Chart
AMINE
EPOXIES POLYAMIDE EPOXIES AMIDOAMINE EPOXIES EPOXYPHENOLICS/NOVOLACS
Description Form very hard, adherent films with excellent chemical and corrosion resistance. Amine cured epoxies are often used as protective coatings and linings in highly corrosive environments. Amine epoxies require care in handling since the amines can be moderately irritating to the skin, and may cause allergic reactions.
Polyamide epoxies generally offer the widest latitude in coating formulation. They are considered more resilient and flexible, and have better weathering resistance and a longer pot life than amine cured epoxies. Polyamide epoxies generally have less solvent and acid resistance than amine cured epoxies.
Amidoamines are reaction products of a polyamine and a fatty acid. Their properties generally fall between those of amines and polyamides. They have good water and corrosion resistance like amines, and good toughness like polyamides. They have relatively small molecular size giving them low viscosities and making them very good surface wetters.
These coatings allow wide range formulating latitude. Novolac epoxy resin increases chemical resistance and solvent resistance. Increasing the level of phenolic increases the chemical and solvent resistance, but the coating loses flexibility. Some phenolics require heat curing.
Advantages • Excellent alkali and water resistance • Very good acid resistance • Excellent solvent resistance • Hard, abrasion resistant film • Excellent corrosion resistance • Excellent wetting of substrate • Chemical/moisture barrier
• Very good alkali and water resistance • Good acid resistance • Longer pot life than amines • Easy to apply
• Cures more quickly than amines • Good weathering characteristics • Good film flexibility • Excellent adhesion
• Excellent surface wetting • Excellent adhesion • Excellent water resistance • Low viscosity
• Longer pot life than amines • Good gloss retention
• High heat resistance • Excellent chemical resistance • Excellent solvent resistance • Excellent corrosion resistance • Hard, abrasion resistant film
Disadvantages/Limitations • Amines can be irritating/toxic • Relatively short recoat time • Relatively short pot life • Slower dry than normal polyamides • Chalks/may discolor
• Faster dry than amines • Chalks
• High viscosity • Temperature dependent • Slow cure
• Slow cure • Fair color retention • Temperature dependent
• Some may require heat cure • Relatively slow air cure • Chalks/may discolor • Relatively brittle
Primary Uses
• Refer to product data sheets for specific use information
• Severe chemical resistant coating
• Barrier coating • Offshore structures • Storage tanks, structural steel • Bridges, power plants • Tank linings • Secondary containment
• Water immersion • General industrial • Offshore structures • Storage tanks, structural steel • Water/wastewater plants • Tank linings
• Bridges, power plants • Secondary containment
• Barrier coating • Surface tolerant coating • Where chemical and moisture resistance is required • General industrial • Refineries • Bridges, power plants
• Severe chemical resistance • Tank linings
• Secondary containment • General industrial • Refineries • Bridges, power plants
Sherwin-Williams Products Amines
Shelcote II Epoxy Shelcote II Flake Filled Dura-Plate UHS Duraplate 301 Tank Clad HS Epoxy Sher-Glass FF Ketimines Macropoxy 920 PrePrime Phenalkamines Dura-Plate 235 Water-Based Water-Based Tile-Clad Kem Cati-Coat HS Filler/Sealer Tile-Clad High Solids Recoatable Epoxy Primer Copoxy Shop Primer Zinc Clad IV Zinc Clad III HS Hi-Solids Catalyzed Epoxy Macropoxy 646 Fast Cure Macropoxy 846 Winter Grade Epolon II Primer
Epolon II Multi-Mil Macropoxy HS Epoxy Pro Industrial High Performance Epoxy
Epoxy Mastic Aluminum II Macropoxy 5500
Phenicon HS Epoxy Phenicon Flake Filled Epo-Phen Nova-Plate UHS Nova-Plate 325 Fast Clad 105ER
Epoxy Coating Comparison Chart
SILOXANE
EPOXIES COAL TAR EPOXIES WATER-BASED EPOXIES EPOXYESTERS
Description Siloxane epoxies are relatively fast curing coatings with excellent stain and mar resistance. They have excellent color and gloss stability. Siloxane epoxies are typically used in high performance industrial applications. Also acceptable for architectural applications.
Coal tar epoxies are a combination of a basic epoxy resin and coal tar. The coal tar is in the form of a semi-liquid pitch and blended with the epoxy resin. The curing agents for coal tar epoxies are usually either amines or polyamides. Coal tar epoxies offer excellent resistance to fresh and salt water and are highly resistant to cathodic disbondment.
Generally consist of a non-yellowing acrylic resin disbursed in water mixed with an emulsified epoxy resin. They are relatively hard, durable coatings with moderate chemical resistance. They offer good stain resistance, abrasion resistance and resistance to most commercial cleaning agents and sanitizers. They can be used over previously applied conventional paints to upgrade the surface for better performance without wrinkling, lifting or bleeding.
A combination of epoxy resin and alkyd resin resulting in an air-drying coating. Epoxy esters provide a hard, durable film ideal as a machinery finish. Recommended for general atmospheric use in areas not considered severely corrosive.
Advantages • Very good weathering resistance
• Hard, abrasion resistant film • Very good acid resistance • Excellent color and gloss retention • Relatively fast dry
• High film build with one coat • Excellent salt water resistance • Excellent water resistance • Excellent resistance to cathodic disbondment • Economical
• Good chemical and solvent resistance • Hard, abrasion resistant film • Upgrades conventional systems to high performance • Water clean-up, low-odor • No strong solvents • Good adhesion • Very long pot-life • Good weathering
• Hard, durable film • Easy to apply • One component • Good moisture resistance • Minimal surface preparation • Moderate cost
• Low temperature application • Increased alkali resistance over alkyds
Disadvantages/Limitations • Solvent resistant • Heat resistant
• Not for potable water • Black color • Critical recoat time/ difficult to recoat • Fair solvent resistance • Chalks/browns
• Flash rusting on ferrous metal unless primed
• Fair solvent resistance • Poor weathering characteristics
• Poor exterior gloss retention
Primary Uses
• Refer to product data sheets for specific use information
• Bridges • Marine • High performance finish coating
• Kennels, schools, jails, hospitals • High moisture areas • Stain resistant coating
• Liner for sewage treatment tanks • Not-potable water tanks • Pipe coating
• Penstocks, dam gates • Offshore rigs • Paper mills • Chemical plants • Secondary containment • Light/moderate industrial areas • Tile-like wall coating • Schools • Hospitals • Food plants • Office areas • Kitchens • Hallways • Nursing homes • Moisture resistance • Where odor or low temperature limitations prevent solvent-based epoxy use
• Abrasion resistance
Sherwin-Williams Products Polysiloxane XLE-80 Hi-Mil Sher-Tar Epoxy TarGuard Coal Tar Epoxy
Water-Based Epoxy Primer Water-Based Epoxy Pro Industrial Hi-Bild Waterbased Epoxy
To learn more, contact us:
North America: 1.800.524.5979
Europe & Middle East: +44 (0)1204 521771
Asia: +8621 51587798
www.sherwin-williams.com/protective
9/14 AD0111 20004096
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